Light guide element for controlling light shape

ABSTRACT

A light guide element for controlling light shape includes a light-incident surface, a light-emitting surface, a first reflecting surface, and a second reflecting surface. The light-incident surface includes a first outer peripheral edge and a first inner peripheral edge. The light-emitting surface includes a second outer peripheral edge and a second inner peripheral edge. The first reflecting surface is constructed by a first profile curve, and connects the first and the second outer peripheral edge. The first profile curve is a connecting line of two points respectively on the first outer peripheral edge and the second outer peripheral edge. The second reflecting surface is constructed by a second profile curve, and connects the first and the second inner peripheral edge. The second profile curve is a connecting line of two points respectively on the first inner peripheral edge and the second inner peripheral edge.

RELATED APPLICATIONS

This application claims priority to Taiwan Application Serial Number102115900, filed May 3, 2013, which is herein incorporated by reference.

BACKGROUND

1. Field of the Invention

The present invention relates to a light guide element, and moreparticularly to a light guide element for controlling a light shape.

2. Description of Related Art

A conventional lamp consists essentially of a bulb and a reflectingmask. The reflecting mask mainly functions to guide light generated fromthe bulb to a required direction and to change light shapes generatedwhile the bulb irradiates. However, the light shapes varied through thereflecting mask have limited diversities, and are usually alight-concentrating type, thus having limited applicability of the lamp.

Another conventional lamp can change a light shape generated from alight source by collaborating with a secondary optical element. However,in this structure, a recess has to be disposed in a center of theoptical element to receive the light source for achieving the object oflight shape adjustment. Thus, the secondary optical element has to matchwith different types or quantities of light sources to change the wholestructure design, thus resulting in cost increase.

Hence, a light guide element is needed to overcome the foregoingproblems.

SUMMARY

One aspect of the present invention is to provide a light guide elementfor controlling a light shape by using a total reflection characteristicof a light beam to change a travel direction of the light beam, thusachieving an object of adjusting the light form emitted from the lightguide element. Therefore, applications of the light guide element maymeet irradiation requirements of various light beam angles, and alsoreduce power consumption.

Another aspect of the present invention is to provide a light guideelement for controlling a light shape by using profile curves to changecurved surface shapes of a first reflecting surface, a second reflectingsurface and a light-emitting surface, thereby adjusting a traveldirection of a light beam in the light guide element to achieve anobject of adjusting the light form emitted from the light guide element.

Another aspect of the present invention is to provide a light guideelement for controlling a light shape by using a Bezier curve functionto define respective profile curves, thus not only simplifyingdefinition rules of respective curved surfaces but also controlling anoverall profile shape of the light guide element in an intuitive manner.

According to the aforementioned objects, the present invention providesa light guide element for controlling a light shape. The light guideelement is suitable for guiding at least one light beam, in which the atleast one light beam is totally reflected in the light guide element togenerate a predetermined light beam angle. The light guide element is anannular frustum and includes a light-incident surface, a light-emittingsurface, a first reflecting surface and a second reflecting surface. Thelight-incident surface has a first outer peripheral edge and a firstinner peripheral edge. The light-emitting surface is opposite to thelight-incident surface and has a second outer peripheral edge and asecond inner peripheral edge. The first reflecting surface connects thefirst outer peripheral edge and the second outer peripheral edge, inwhich the first reflecting surface is a curved surface constructed by afirst profile curve. The first profile curve is a connecting line from afirst initial point on the first outer peripheral edge to a firstterminating point on the second outer peripheral edge. The secondreflecting surface connects the first inner peripheral edge and thesecond inner peripheral edge, in which the second reflecting surface isa curved surface constructed by a second profile curve. The secondprofile curve is a connecting line from a second initial point on thefirst inner peripheral edge to a second terminating point on the secondinner peripheral edge.

According to an embodiment of the present invention, the first profilecurve is defined by a Bezier curve function,

${B(t)} = {\frac{\sum\limits_{i = 0}^{n}{\begin{pmatrix}n \\i\end{pmatrix}{t^{i}\left( {1 - t} \right)}^{n - i}P_{i}W_{i}}}{\sum\limits_{i = 0}^{n}{\begin{pmatrix}n \\i\end{pmatrix}{t^{i}\left( {1 - t} \right)}^{n - i}W_{i}}}.}$

There is at least one first control point between the first initialpoint and the first terminating point. “P_(i)” represents a positioncoordinate of an i^(th) point in the Bezier curve function, in whichwhen a total number of at least one first control point is one, aposition coordinate of the first initial point is (X₀,Y₀), a positioncoordinate of the first control point is (X₁,Y₁) and a positioncoordinate of the first terminating point is (X₂,Y₂). “n” represents thetotal number of the at least one first control point plus 1. “W_(i)”represents a weight of the i^(th) point. “t” represents a ratio of alength between a predetermined point and the first initial point to atotal length of the first profile curve. Constraints of the firstprofile curve are:

X₀ ≦ X₁ ≦ X₂; 90^(∘) ≧ α₁ ≧ α₂; 0 ≦ α₁ = θ₁ + θ₂ − 90^(∘);${\theta_{1} = {\sin^{- 1}\left( \frac{1}{n_{material}} \right)}};{\theta_{2} \geqq {{90{^\circ}} - \theta_{1}}};{and}$0 ≦ W_(i) ≦ 1.

α₁ represents an angle included between a horizontal line and aconnecting line from the first initial point to the at least one firstcontrol point α₂ represents an angle included between a horizontal lineand a connecting line from the first initial point to the firstterminating point. θ₁ represents a refracting angle of the at least onelight beam entering from outside of the light guide element. θ₂represents an incident angle of the at least one light beam which isincident toward the first reflecting surface after entering the lightguide element. n_(material) represents a refractive index of the lightguide element.

According to another embodiment of the present invention, the secondprofile curve is defined by a Bezier curve function,

${B(t)} = {\frac{\sum\limits_{i = 0}^{n}{\begin{pmatrix}n \\i\end{pmatrix}{t^{i}\left( {1 - t} \right)}^{n - i}P_{i}W_{i}}}{\sum\limits_{i = 0}^{n}{\begin{pmatrix}n \\i\end{pmatrix}{t^{i}\left( {1 - t} \right)}^{n - i}W_{i}}}.}$

There is at least one second control point between the second initialpoint and the second terminating point. “P_(i)” represents a positioncoordinate of an i^(th) point in the Bezier curve function, in whichwhen a total number of at least one second control point is one, aposition coordinate of the second initial point is (X′₀,Y′₀), a positioncoordinate of the second control point is (X′₁,Y′₁) and a positioncoordinate of the second terminating point is (X′₂,Y′₂). “n” representsthe total number of the at least one second control point plus 1.“W_(i)” represents a weight of the i^(th) point. “t” represents a ratioof a length between a predetermined point and the second initial pointto a total length of the second profile curve. Constraints of the secondprofile curve are:

X₀^(′) ≦ X₁^(′) ≦ X₂^(′); 90^(∘) ≧ α₁^(′) ≧ α₂^(′); 0 ≦ α₁^(′) = θ₁^(′) + θ₂^(′) − 90^(∘);${\theta_{1}^{\prime} = {\sin^{- 1}\left( \frac{1}{n_{material}} \right)}};{\theta_{2}^{\prime} \geqq {{90{^\circ}} - \theta_{1}^{\prime}}};{and}$0 ≦ W_(i) ≦ 1.

α₁′ represents an angle included between a horizontal line and aconnecting line from the second initial point to the at least one secondcontrol point. α₂′ represents an angle included between a horizontalline and a connecting line from the second initial point to the secondterminating point. θ₁′ represents a refracting angle of the at least onelight beam entering from outside of the light guide element. θ₂′represents an incident angle of the at least one light beam which isincident toward the second reflecting surface after entering the lightguide element. n_(material) represents a refractive index of the lightguide element.

According to another embodiment of the present invention, the firstprofile curve and the second profile curve have the same profile ordifferent profiles.

According to another embodiment of the present invention, thelight-emitting surface is defined by a third profile curve, in which thethird profile curve is a connecting line from a third initial point onthe second outer peripheral edge to a third terminating point on thesecond inner peripheral edge.

According to another embodiment of the present invention, the thirdprofile curve is defined by a Bezier curve function,

${B(t)} = {\frac{\sum\limits_{i = 0}^{n}{\begin{pmatrix}n \\i\end{pmatrix}{t^{i}\left( {1 - t} \right)}^{n - i}P_{i}W_{i}}}{\sum\limits_{i = 0}^{n}{\begin{pmatrix}n \\i\end{pmatrix}{t^{i}\left( {1 - t} \right)}^{n - i}W_{i}}}.}$

There is at least one third control point between the third initialpoint and the third terminating point. “P_(i)” represents a positioncoordinate of an i^(th) point in the Bezier curve function, in whichwhen a total number of at least one third control point is one, aposition coordinate of the third initial point is (X₃,Y₃), a positioncoordinate of the third control point is (X₄,Y₄) and a positioncoordinate of the third terminating point is (X₅,Y₅). “n” represents thetotal number of the at least one third control point plus 1. “W_(i)”represents a weight of the i^(th) point. “t” represents a ratio of alength between a predetermined point and the third initial point to atotal length of the third profile curve. Constraints of the secondprofile curve are: X₃=X₅; Y₃≧Y₄≧Y₅; and 0≦W_(i)≦1.

According to another embodiment of the present invention, the firstreflecting surface is formed from a plurality of first reflecting curvedsurfaces, in which each of the first reflecting curved surfaces isconstructed by the first profile curve.

According to another embodiment of the present invention, the secondreflecting surface is formed from a plurality of second reflectingcurved surfaces, in which each of the second reflecting curved surfacesis constructed by the second profile curve.

According to the aforementioned objects, the present invention providesa lamp. The lamp includes a light guide element and a light source. Thelight guide element is an annular frustum and includes a light-incidentsurface, a light-emitting, a first reflecting surface and a secondreflecting surface. The light-incident surface has a first outerperipheral edge and a first inner peripheral edge. The light-emittingsurface is opposite to the light-incident surface and has a second outerperipheral edge and a second inner peripheral edge. The first reflectingsurface connects the first outer peripheral edge and the second outerperipheral edge, in which the first reflecting surface is a curvedsurface constructed by a first profile curve. The first profile curve isa connecting line from a first initial point on the first outerperipheral edge to a first terminating point on the second outerperipheral edge. The second reflecting surface connects the first innerperipheral edge and the second inner peripheral edge, in which thesecond reflecting surface is a curved surface constructed by a secondprofile curve. The second profile curve is a connecting line from asecond initial point on the first inner peripheral edge to a secondterminating point on the second inner peripheral edge. A light generatedfrom the light source enters the light guide element from thelight-incident surface and emits out of the light-emitting surface togenerate a predetermined light beam angle of the light.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the followingdetailed description of the embodiment, with reference made to theaccompanying drawings as follows:

FIG. 1A is a schematic structural diagram showing a light guide elementin accordance with a first embodiment of the present invention;

FIG. 1B is a schematic cross-sectional view of the light guide elementviewed along a line A-A in FIG. 1A;

FIG. 2A is a schematic structural diagram showing a light guide elementin accordance with a second embodiment of the present invention;

FIG. 2B is a schematic cross-sectional view of the light guide elementviewed along a line B-B in FIG. 2A;

FIG. 2C is a schematic diagram of a first profile curve in accordancewith the second embodiment of the present invention;

FIG. 2D is a candlepower distribution curve generated from the lightguide element in accordance with the second embodiment of the presentinvention;

FIG. 3A is a schematic structural diagram showing a light guide elementin accordance with a third embodiment of the present invention;

FIG. 3B is a schematic cross-sectional view of the light guide elementviewed along a line C-C in FIG. 3A;

FIG. 3C is a schematic diagram of a first profile curve in accordancewith the third embodiment of the present invention;

FIG. 3D is a candlepower distribution curve generated from the lightguide element in accordance with the third embodiment of the presentinvention;

FIG. 4A is a schematic structural diagram showing a light guide elementin accordance with a fourth embodiment of the present invention;

FIG. 4B is a schematic cross-sectional view of the light guide elementviewed along a line D-D in FIG. 4A;

FIG. 4C is a schematic diagram of a first profile curve in accordancewith the fourth embodiment of the present invention;

FIG. 4D is a candlepower distribution curve generated from the lightguide element in accordance with the fourth embodiment of the presentinvention;

FIG. 5A is a schematic structural diagram showing a light guide elementin accordance with a fifth embodiment of the present invention;

FIG. 5B is a schematic cross-sectional view of the light guide elementviewed along a line E-E of FIG. 5A;

FIG. 5C is a schematic diagram of a first profile curve in accordancewith the fifth embodiment of the present invention;

FIG. 5D is a candlepower distribution curve generated from the lightguide element in accordance with the fifth embodiment of the presentinvention;

FIG. 6A is a schematic structural diagram showing a light guide elementin accordance with a first example of a sixth embodiment of the presentinvention;

FIG. 6B is a candlepower distribution curve generated from the lightguide element in accordance with the first example of the sixthembodiment of the present invention;

FIG. 7A is a schematic structural diagram showing a light guide elementin accordance with a second example of the sixth embodiment of thepresent invention;

FIG. 7B is a candlepower distribution curve generated from the lightguide element in accordance with the second example of the sixthembodiment of the present invention;

FIG. 8A is a schematic structural diagram showing a light guide elementin accordance with a third example of the sixth embodiment of thepresent invention;

FIG. 8B is a candlepower distribution curve generated from the lightguide element in accordance with the third example of the sixthembodiment of the present invention;

FIG. 9A is a schematic structural diagram showing a light guide elementin accordance with a fourth example of the sixth embodiment of thepresent invention;

FIG. 9B is a candlepower distribution curve generated from the lightguide element in accordance with the fourth example of the sixthembodiment of the present invention;

FIG. 10A is a schematic structural diagram showing a light guide elementin accordance with a fifth example of the sixth embodiment of thepresent invention; and

FIG. 10B is a candlepower distribution curve generated from the lightguide element in accordance with the fifth example of the sixthembodiment of the present invention.

DETAILED DESCRIPTION

Referring to FIGS. 1A and 1B, FIG. 1A is a schematic structural diagramof a light guide element 100 in accordance with a first embodiment, andFIG. 18B is a schematic cross-sectional view of the light guide element100 viewed along a line A-A in FIG. 1A. In the present embodiment, thelight guide element 100 is suitable for use in guiding a light beam andenabling the light beam to be totally reflected in the light guideelement 100, so as to generate different light beam angles. In thepresent embodiment, the light beam may come from a light source, such asa light emitting diode (LED). The light guide element 100 is an annularfrustum having a through hole 110. The light guide element 100 includesa light-incident surface 112, a light-emitting surface 114, a firstreflecting surface 116 and a second reflecting surface 118. The throughhole 110 forms a first opening 110 a on the light-incident surface 112,and the light-incident surface 112 has a first outer peripheral edge 112a and a first inner peripheral edge 112 b. The light-emitting surface114 is opposite to the light-incident surface 112. The through hole 110forms a second opening 110 b on the light-emitting surface 114, and thelight-emitting surface 114 has a second outer peripheral edge 114 a anda second inner peripheral edge 114 b.

The first reflecting surface 116 connects the first outer peripheraledge 112 a and the second outer peripheral edge 114 a, and the firstreflecting surface 116 is a curved surface constructed by a firstprofile curve B1. The first profile curve B1 is a connecting line from afirst initial point on the first outer peripheral edge 112 a to a firstterminating point on the second outer peripheral edge 114 a. It is notedthat the first profile curve B1 in the present embodiment is a curve ofintersection between the first reflecting surface 116 and any cut planewhich is perpendicular to the light-incident surface 112 and passesthrough a center of the light guide element 100. The second reflectingsurface 118 connects the first inner peripheral edge 112 b and thesecond inner peripheral edge 114 b, and the second reflecting surface118 is a curved surface constructed by a second profile curve B2. Thesecond profile curve B2 is a connecting line from a second initial pointon the first inner peripheral edge 112 b to a second terminating pointon the second inner peripheral edge 114 b. Similarly, the second profilecurve B2 in the present embodiment is a curve of intersection betweenthe second reflecting surface 118 and any cut plane which isperpendicular to the light-incident surface 112 and passes through thecenter of the light guide element 100.

In one embodiment, the first profile curve B1 is defined by a Beziercurve function. Bezier curves are various curves illustrated mainly byusing three or more points of position coordinates with differentweights according to the Bezier curve function. The Bezier curvefunction is shown as

$\begin{matrix}{{B(t)} = {\frac{\sum\limits_{i = 0}^{n}{\begin{pmatrix}n \\i\end{pmatrix}{t^{i}\left( {1 - t} \right)}^{n - i}P_{i}W_{i}}}{\sum\limits_{i = 0}^{n}{\begin{pmatrix}n \\i\end{pmatrix}{t^{i}\left( {1 - t} \right)}^{n - i}W_{i}}}.}} & (1)\end{matrix}$

where “P_(i)” represents a position coordinate of an i^(th) point in theBezier curve function. In the present embodiment, there is at least onefirst control point between the first initial point and the firstterminating point. For example, when a total number of the at least onefirst control point is one, the first control point P₁ is locatedbetween the first initial point P₀ and the first terminating point P₂.The position of the first control point is mainly used for determining aradian of the first profile curve B1. For example, when a total numberof the at least one first control point is one, a position coordinate ofthe first initial point P₀ is (X₀,Y₀), a position coordinate of thefirst control point P₁ is (X₁,Y₁), and a position coordinate of thefirst terminating point P₂ is (X₂,Y₂). In the Bezier curve function, “n”represents the total number of the at least one first control point plus1, and “W_(i)” represents a weight of a point P_(i). For example, whenthe total number of the at least one first control point is 2, “n” is 3.In addition, “W₁” represents a weight of the first control point P₁which can adjust the shape of the first profile curve B1. As shown inFIG. 1B, the weight W₁ in a connecting line from the first initial pointP₀ to the first control point P₁ is defined as 1, and the weight W₁ in aconnecting line from the first initial point P₀ to the first terminatingpoint P₂ is defined as 0. If the weight of the first control point P₁approaches 1, the first profile curve B1 will trend to the connectingline from the first initial point P₀ to the first control point P₁.Similarly, if the weight of the first control point P₁ approaches 0, thefirst profile curve B1 will trend to the connecting line from the firstinitial point P₀ to the first terminating point P₂. In the Bezier curvefunction, “t” represents a ratio of a length between a predeterminedpoint and the first initial point to a total length of the first profilecurve B1. The aforementioned “total length” is a length of theconnecting line from the first initial point to the first terminatingpoint. Therefore, “t” may represent a corresponding value of a positionof any point on the first profile curve B1 between the first initialpoint and the first terminating point.

After the first initial point P₀, the first control point P₁ and thefirst terminating point P₂ are defined, the first profile curve B1 arefurther defined by constraints shown as:

$\begin{matrix}{{{X_{0} \leqq X_{1} \leqq X_{2}};}{{{90{^\circ}} \geqq \alpha_{1} \geqq \alpha_{2}};}{{{0 \leqq \alpha_{1}} = {\theta_{1} + \theta_{2} - {90{^\circ}}}};}{{\theta_{1} = {\sin^{- 1}\left( \frac{1}{n_{material}} \right)}};}{{\theta_{2} \geqq {{90{^\circ}} - \theta_{1}}};{and}}{0 \leqq W_{i} \leqq 1.}} & (2)\end{matrix}$

Referring to FIG. 1B again, α₁ represents an angle included between ahorizontal line and the connecting line from the first initial point P₀to the first control point P₁. α₂ represents an angle included between ahorizontal line and the connecting line from the first initial point P₀to the first terminating point P₂. θ₁ represents a refracting angle ofthe light beam entering from outside of the light guide element 100. θ₂represents an incident angle of the light beam which is incident towardthe first reflecting surface 116 after entering the light guide element100. n_(material) represents a refractive index of the light guideelement 100. Therefore, adjusting each parameter value of theconstraints may change the shape of the first reflecting surface 116.

Referring to FIGS. 1A and 1B again, in one embodiment, the secondprofile curve B2 may be the same curve as the first profile curve B1.Both the first profile curve B1 and the second profile curve B2 aredefined by the aforementioned Bezier curve function. For clarity ofexplanation, P′_(i), X′_(i), and Y′_(i), are used below to representP_(i), X_(i) and Y_(i) in equations (1) and (2).

In the present embodiment, there is at least one second control pointbetween the second initial point and the second terminating point. Forexample, when a total number of the at least one first control point isone, the second control point P′₁ is located between the second initialpoint P′₀ and the second terminating point P′₂. The position of thesecond control point is mainly used for determining a radian of thesecond profile curve B2. For example, when a total number of the atleast one second control point is one, a position coordinate of thesecond initial point P′₀ is (X′₀,Y′₀), a position coordinate of thesecond control point P′₁ is (X′₁,Y′₁), and a position coordinate of thesecond terminating point P′₂ is (X′₂,Y′₂). In the Bezier curve function,“n” represents the total number of the at least one second control pointplus 1. In addition, “W_(i)” represents a weight of the second controlpoint P′_(i) which can adjust the shape of the second profile curve B2.As shown in FIG. 1B, the weight W₁ in a connecting line from the secondinitial point P′₀ to the second control point P′₁ is defined as 1, andthe weight W₁ in a connecting line from the second initial point P′₀ tothe second terminating point P′₂ is defined as 0. If the weight of thesecond control point P′₁ approaches 1, the second profile curve B2 willtrend to the connecting line from the second initial point P′₀ to thesecond control point P′₁. Similarly, if the weight of the second controlpoint P′₁ approaches 0, the second profile curve B2 will trend to theconnecting line from the second initial point P′₀ to the secondterminating point P′₂. In the Bezier curve function, “t” represents aratio of a length between a predetermined point and the second initialpoint to a total length of the second profile curve B2. Theaforementioned “total length” is a length of the connecting line fromthe second initial point to the second terminating point. Therefore, “t”may represent a corresponding value of a position of any point on thesecond profile curve B2 between the second initial point and the secondterminating point.

After the second initial point P′₀, the second control point P′₁ and thesecond terminating point P′₂, are defined, the second profile curve B2are further defined by constraints shown as:

$\begin{matrix}{{{X_{0}^{\prime} \leqq X_{1}^{\prime} \leqq X_{2}^{\prime}};}{{{90{^\circ}} \geqq \alpha_{1}^{\prime} \geqq \alpha_{2}^{\prime}};}{{{0 \leqq \alpha_{1}^{\prime}} = {\theta_{1}^{\prime} + \theta_{2}^{\prime} - {90{^\circ}}}};}{{\theta_{1}^{\prime} = {\sin^{- 1}\left( \frac{1}{n_{material}} \right)}};}{{\theta_{2}^{\prime} \geqq {{90{^\circ}} - \theta_{1}^{\prime}}};{and}}{0 \leqq W_{i} \leqq 1.}} & (3)\end{matrix}$

Referring to FIG. 1B again, α₁′ represents an angle included between ahorizontal line and the connecting line from the second initial pointP₀′ to the first control point P′₁. α₂′ represents an angle includedbetween a horizontal line and the connecting line from the secondinitial point P′₀ to the second terminating point P′₂. θ₁′ represents arefracting angle of the light beam entering from outside of the lightguide element 100. θ₂′ represents an incident angle of the light beamwhich is incident toward the second reflecting surface 118 afterentering the light guide element 100. n_(material) represents arefractive index of the light guide element 100. Therefore, adjustingeach parameter value of the constraints may change the shape of thesecond reflecting surface 118.

It can be known from the above descriptions that, the second profilecurve B2 is defined by the same Bezier curve function and the sameconstraints for the first profile curve B1. Therefore, in oneembodiment, the second profile curve B2 and the first profile curve B1can have the same profile, so that the second reflecting surface 118 andthe first reflecting surface 116 are symmetrical. However, in anotherembodiment, the second profile curve B2 and the first profile curve B1may have different profiles defined by different parameter values, sothat the second reflecting surface 118 and the first reflecting surface116 are not symmetrical.

Referring to FIG. 2A to FIG. 2D, FIG. 2A is a schematic structuraldiagram a light guide element 200 in accordance with a second embodimentof the present invention; FIG. 2B is a schematic cross-sectional view ofthe light guide element 200 viewed along a line B-B in FIG. 2A; FIG. 2Cis a schematic diagram of a first profile curve in accordance with thesecond embodiment of the present invention; and FIG. 2D is a candlepowerdistribution curve generated from the light guide element in accordancewith the second embodiment of the present invention.

In the second embodiment, as shown in FIG. 2C, the first profile curveB1 of the light guide element 200 is formed from the parameter valueswhich are P₀=(0,0), P₁=(21.3,13), P₂=(36,8.5) and W₁=0.45. The secondprofile curve B2 and the first profile curve B1 are symmetrical. Asshown in FIG. 2B, the light beam enters the light guide element 200 froma light-incident surface 212, and is reflected out of the light-emittingsurface 214 by the light guide element 200. In the present embodiment,the light beam is emitted from the light guide element 200 at a lightbeam angle of about 82 degrees.

Referring to FIG. 3A to FIG. 3D, FIG. 3A is a schematic structuraldiagram of a light guide element 300 in accordance with a thirdembodiment of the present invention; FIG. 3B is a schematiccross-sectional view of the light guide element 300 viewed along a lineC-C in FIG. 3A; FIG. 3C is a schematic diagram of a first profile curvein accordance with the third embodiment of the present invention; andFIG. 3D is a candlepower distribution curve generated from the lightguide element in accordance with the third embodiment of the presentinvention.

In the third embodiment, as shown in FIG. 3C, the first profile curve B1of the light guide element 300 is formed from the parameter values whichare P₀=(0,0), P₁=(7.6,4.6), P₂=(36,8.5) and W₁=0.45. The second profilecurve B2 and the first profile curve B1 are symmetrical. As shown inFIG. 3B, the light beam enters the light guide element 300 from alight-incident surface 312, and is reflected out of the light-emittingsurface 314 by the light guide element 300. In the present embodiment,the light beam is emitted from the light guide element 300 at a lightbeam angle of about 24 degrees.

Referring to FIG. 4A to FIG. 4D, FIG. 4A is a schematic structuraldiagram of a light guide element 400 in accordance with a fourthembodiment of the present invention; FIG. 4B is a schematiccross-sectional view of the light guide element 400 viewed along a lineD-D in FIG. 4A; FIG. 4C is a schematic diagram of a first profile curvein accordance with the fourth embodiment of the present invention; andFIG. 4D is a candlepower distribution curve generated from the lightguide element in accordance with the fourth embodiment of the presentinvention.

In the fourth embodiment, as shown in FIG. 4C, the first profile curveB1 of the light guide element 400 is formed from the parameter valueswhich are P₀=(0,0), P₁=(24.6,17.2), P₂=(36,8.5) and W₁=0.45. The secondprofile curve B2 and the first profile curve B1 are symmetrical. Asshown in FIG. 4B, the light beam enters the light guide element 400 froma light-incident surface 412, and is reflected out of the light-emittingsurface 414 by the light guide element 400. In the present embodiment,the light beam is emitted from the light guide element 400 at a lightbeam angle of about 93 degrees.

Referring to FIG. 5A to FIG. 5D, FIG. 5A is a schematic structuraldiagram of a light guide element 500 in accordance with a fifthembodiment of the present invention; FIG. 5B is a schematiccross-sectional view of the light guide element 500 viewed along a lineE-E in FIG. 5A; FIG. SC is a schematic diagram of a first profile curvein accordance with the fifth embodiment of the present invention; andFIG. 5D is a candlepower distribution curve generated from the lightguide element in accordance with the fifth embodiment of the presentinvention.

In the fifth embodiment, the light guide element 500 is similar to thelight guide element 100. The light guide element 500 includes alight-incident surface 512, a light-emitting surface 514, a firstreflecting surface 516 and a second reflecting surface 518. The firstreflecting surface 516 and the second reflecting surface 518 are similarto the first reflecting surface 116 and the second reflecting surface118. The first reflecting surface 516 and the second reflecting surface518 are constructed by the same first profile curve B1 and the samesecond profile curve B2 which are described before, and will not berepeated herein. In the present embodiment, the light-emitting surface514 has an outer peripheral edge 514 a and an inner peripheral edge 514b. The light-emitting surface 514 is constructed by a third profilecurve B3. The third profile curve B3 is a connecting line from a thirdinitial point on the outer peripheral edge 514 a to a third terminatingpoint on the inner peripheral edge 514 b.

It is noted that the third profile curve B3 in the present embodiment isa curve of intersection between the light-emitting surface 514 and anycut plane which is perpendicular to the light-incident surface 512 andpasses through a center of the light guide element 500. In oneembodiment, the third profile curve B3 and the first profile curve B1may be defined by the same profile curve. Both the first profile curveB1 and the third profile curve B3 are defined by the aforementionedBezier curve function.

In the present embodiment, there is at least one third control pointbetween the third initial point and the third terminating point. Forexample, when a total number of the at least one third control point isone, the third control point P₄ is located between the third initialpoint P₃ and the third terminating point P₅. The position of the thirdcontrol point is mainly used for determining a radian of the thirdprofile curve B3. For example, when a total number of the at least onethird control point is one, a position coordinate of the third initialpoint P₃ is (X₃,Y₃), a position coordinate of the third control point P₄is (X₄,Y₄), and a position coordinate of the third terminating point P₅is (X₅,Y₅). In the Bezier curve function, the definition of “P_(i)”,“n”, “W_(i)” and “t” are described in the above descriptions, and willnot be described again. After the third initial point P₃, the thirdcontrol point P₄ and the third terminating point P₅ are defined, thethird profile curve B3 are further defined by constraints shown asX₃=X₅; Y₃≧Y₄≧Y₅; and 0≦W_(i)≦1.

Referring to FIG. 5A to FIG. 5D again, in the fifth embodiment, thefirst profile curve B1 and the second profile curve B2 are formed fromthe same parameter values of the third embodiment, i.e. P₀=(0,0),P₁=(7.6,4.6), P₂=(36,8.5) and W₁=0.45. As shown in FIG. 5C, the thirdprofile curve B3 of the light guide element 500 is formed from theparameter values which are P₃=(0,21), P₄=(10.6,10.6), P₅=(0,0) andW₄=0.45. As shown in FIG. 5B, the light beam enters the light guideelement 500 from a light-incident surface 512, and is reflected out ofthe light-emitting surface 514 by the light guide element 500. In thepresent embodiment, the light beam is emitted from the light guideelement 500 at a light beam angle of about 13 degrees. Therefore, fromthe first embodiment to the fifth embodiment above, adjusting eachparameter value of the constraints may change the shape of thelight-emitting surface 514.

Referring to FIG. 6A and FIG. 6B, FIG. 6A is a schematic structuraldiagram a light guide element 600 in accordance with a first example ofa sixth embodiment of the present invention; and FIG. 6B is acandlepower distribution curve generated from the light guide element600 in accordance with the first example of the sixth embodiment of thepresent invention. In the present embodiment, the light guide element600 includes a light-incident surface 612, a light-emitting surface 614,a first reflecting surface 616 and a second reflecting surface 618. Thefirst reflecting surface 616 is formed from six first reflecting curvedsurfaces. Each of these first reflecting curved surfaces is constructedby the first profile curve B1. Similarly, the second reflecting surface618 is formed from six second reflecting curved surfaces. Each of thesesecond reflecting curved surfaces is constructed by the second profilecurve B2.

Referring to FIG. 7A and FIG. 7B, FIG. 7A is a schematic structuraldiagram a light guide element 700 in accordance with a second example ofthe sixth embodiment of the present invention; and FIG. 7B is acandlepower distribution curve generated from the light guide element700 in accordance with the second example of the sixth embodiment of thepresent invention. In the present embodiment, the light guide element700 includes a light-incident surface 712, a light-emitting surface 714,a first reflecting surface 716 and a second reflecting surface 718. Thefirst reflecting surface 716 is formed from eight first reflectingcurved surfaces. Each of these first reflecting curved surfaces isconstructed by the first profile curve B1. Similarly, the secondreflecting surface 618 is formed from eight second reflecting curvedsurfaces. Each of these second reflecting curved surfaces is constructedby the second profile curve B2.

Referring to FIG. 8A and FIG. 8B, FIG. 8A is a schematic structuraldiagram of a light guide element 800 in accordance with a third exampleof the sixth embodiment of the present invention; and FIG. 8B is acandlepower distribution curve generated from the light guide element800 in accordance with the third example of the sixth embodiment of thepresent invention. In the present embodiment, the light guide element800 includes a light-incident surface 812, a light-emitting surface 814,a first reflecting surface 816 and a second reflecting surface 818. Thefirst reflecting surface 816 is formed from twelve first reflectingcurved surfaces. Each of these first reflecting curved surfaces isconstructed by the first profile curve B1. Similarly, the secondreflecting surface 618 is formed from twelve second reflecting curvedsurfaces. Each of these second reflecting curved surfaces is constructedby the second profile curve B2.

From the above, different shapes of the light guide elements, such aslight guide element 600,700 and 800 may form different light beamangles. It is noted that the number of the first reflecting curvedsurfaces and the second reflecting curved surfaces are described thesame, it is possible to utilize different number of the first reflectingcurved surfaces and the second reflecting curved surfaces. Additionally,the first profile curve B1 and the second profile curve B2 may bedefined by the same profile curve or different profile curves. Thefollowing examples are directed to other modifications of the lightguide element 600 of the sixth embodiment.

Referring to FIG. 9A and FIG. 9B, FIG. 9A is a schematic structuraldiagram of a light guide element 600 a in accordance with a fourthexample of the sixth embodiment of the present invention; and FIG. 9B isa candlepower distribution curve generated from the light guide element600 a in accordance with the fourth example of the sixth embodiment ofthe present invention. In the present embodiment, the first profilecurve B1 of the light guide element 600 a is formed from the parametervalues which are P₀=(0,0), P₁=(10.3,6.2), P₂=(36,8.5) and W₁=0.45. Thesecond profile curve B2 and the first profile curve B1 are symmetrical.In the present embodiment, the light beam is emitted from the lightguide element 600 a at a light beam angle of about 47 degrees.

Referring to FIG. 10A and FIG. 10B, FIG. 10A is a schematic structuraldiagram of a light guide element 600 b in accordance with a fifthexample of the sixth embodiment of the present invention; and FIG. 10Bis a candlepower distribution curve generated from the light guideelement 600 b in accordance with the fifth example of the sixthembodiment of the present invention. In the present embodiment, thefirst profile curve B1 of the light guide element 600 b is formed fromthe parameter values which are P₀=(0,0), P₁=(32.8,22.9), P₂=(36,8.5) andW₁=0.45. The second profile curve B2 is formed from the parameter valueswhich are P′₀=(0,0), P′₁=(10,15), P′₂=(36,8.5) and W₁=0. In the presentembodiment, the light beam is emitted from the light guide element 600 bat a light beam angle of about 63 degrees.

According to the aforementioned embodiments of the present invention,one advantage of the present invention is using profile curves to changecurved surface shapes of a first reflecting surface, a second reflectingsurface and a light-emitting surface of a light guide element, therebyadjusting a travel direction of the light beam in the light guideelement to achieve an object of adjusting the light form emitted fromthe light guide element. Furthermore, by using a total reflectioncharacteristic of the light beam to change a travel direction of thelight beam can achieve an object of adjusting the light form emittedfrom the light guide element. Therefore, the applications of the lightguide element may meet irradiation requirements of various light beamangles, and also reduce power consumption. Additionally, using theBezier curve function to define respective profile curves can not onlysimplify definition rules of respective curved surfaces but also cancontrol an overall profile shape of the light guide element in anintuitive manner.

Although the present invention has been described in considerable detailwith reference to certain embodiments thereof, other embodiments arepossible. Therefore, the spirit and scope of the appended claims shouldnot be limited to the description of the embodiments contained herein.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims.

What is claimed is:
 1. A light guide element for controlling a lightshape, suitable for guiding at least one light beam, wherein the atleast one light beam is totally reflected in the light guide element togenerate a predetermined light beam angle, and the light guide elementis an annular frustum and comprises: a light-incident surface having afirst outer peripheral edge and a first inner peripheral edge; alight-emitting surface which is opposite to the light-incident surfaceand has a second outer peripheral edge and a second inner peripheraledge; a first reflecting surface connecting the first outer peripheraledge and the second outer peripheral edge, wherein the first reflectingsurface is a curved surface constructed by a first profile curve,wherein the first profile curve is a connecting line from a firstinitial point on the first outer peripheral edge to a first terminatingpoint on the second outer peripheral edge; and a second reflectingsurface connecting the first inner peripheral edge and the second innerperipheral edge, wherein the second reflecting surface is a curvedsurface constructed by a second profile curve, wherein the secondprofile curve is a connecting line from a second initial point on thefirst inner peripheral edge to a second terminating point on the secondinner peripheral edge.
 2. The light guide element of claim 1, whereinthe first profile curve is defined by a Bezier curve function,${{B(t)} = \frac{\sum\limits_{i = 0}^{n}{\begin{pmatrix}n \\i\end{pmatrix}{t^{i}\left( {1 - t} \right)}^{n - i}P_{i}W_{i}}}{\sum\limits_{i = 0}^{n}{\begin{pmatrix}n \\i\end{pmatrix}{t^{i}\left( {1 - t} \right)}^{n - i}W_{i}}}};$ there isat least one first control point between the first initial point and thefirst terminating point; P_(i) represents a position coordinate of ani^(th) point in the Bezier curve function; when a total number of atleast one first control point is one, a position coordinate of the firstinitial point is (X₀,Y₀); a position coordinate of the first controlpoint is (X₁,Y₁); and a position coordinate of the first terminatingpoint is (X₂,Y₂); wherein n represents the total number of the at leastone first control point plus 1; W_(i) represents a weight of the i^(th)point; and t represents a ratio of a length between a predeterminedpoint and the first initial point to a total length of the first profilecurve; wherein constraints of the first profile curve are X₀ ≦ X₁ ≦ X₂;90^(∘) ≧ α₁ ≧ α₂; 0 ≦ α₁ = θ₁ + θ₂ − 90^(∘);${\theta_{1} = {\sin^{- 1}\left( \frac{1}{n_{material}} \right)}};$θ₂ ≧ 90^(∘) − θ₁; and 0 ≦ W_(i) ≦ 1; wherein α₁ represents an angleincluded between a horizontal line and a connecting line from the firstinitial point to the at least one first control point; α₂ represents anangle included between a horizontal line and a connecting line from thefirst initial point to the first terminating point, θ₁ represents arefracting angle of the at least one light beam entering from outside ofthe light guide element; θ₂ represents an incident angle of the at leastone light beam which is incident toward the first reflecting surfaceafter entering the light guide element, and n_(material) represents arefractive index of the light guide element.
 3. The light guide elementof claim 1, wherein the second profile curve is defined by a Beziercurve function,${{B(t)} = \frac{\sum\limits_{i = 0}^{n}{\begin{pmatrix}n \\i\end{pmatrix}{t^{i}\left( {1 - t} \right)}^{n - i}P_{i}W_{i}}}{\sum\limits_{i = 0}^{n}{\begin{pmatrix}n \\i\end{pmatrix}{t^{i}\left( {1 - t} \right)}^{n - i}W_{i}}}};$ there isat least one second control point between the second initial point andthe second terminating point; P_(i) represents a position coordinate ofan i^(th) point in the Bezier curve function; when a total number of atleast one second control point is one, a position coordinate of thesecond initial point is (X′₀,Y′₀); a position coordinate of the at leastone second control point is (X′₁,Y′₁); and a position coordinate of thesecond terminating point is (X′₂,Y′₂); wherein n represents the totalnumber of the at least one second control point plus 1, W_(i) representsa weight of the i^(th) point; and t represents a ratio of a lengthbetween a predetermined point and the second initial point to a totallength of the second profile curve; wherein constraints of the secondprofile curve are X₀^(′) ≦ X₁^(′) ≦ X₂^(′); 90^(∘) ≧ α₁^(′) ≧ α₂^(′);0 ≦ α₁^(′) = θ₁^(′) + θ₂^(′) − 90^(∘);${\theta_{1}^{\prime} = {\sin^{- 1}\left( \frac{1}{n_{material}} \right)}};$θ₂^(′) ≧ 90^(∘) − θ₁^(′); and 0 ≦ W_(i) ≦ 1; wherein α₁′ represents anangle included between a horizontal line and a connecting line from thesecond initial point to the at least one second control point; α₂′represents an angle included between a horizontal line and a connectingline from the second initial point to the second terminating point, θ₁′represents a refracting angle of the at least one light beam enteringfrom outside of the light guide element; θ₂′ represents an incidentangle of the at least one light beam which is incident toward the secondreflecting surface after entering the light guide element, andn_(material) represents a refractive index of the light guide element.4. The light guide element of claim 1, wherein the first profile curveand the second profile curve have the same profile or differentprofiles.
 5. The light guide element of claim 1, wherein thelight-emitting surface is defined by a third profile curve, wherein thethird profile curve is a connecting line from a third initial point onthe second outer peripheral edge to a third terminating point on thesecond inner peripheral edge.
 6. The light guide element of claim 5,wherein the third profile curve is defined by a Bezier curve function,${{B(t)} = \frac{\sum\limits_{i = 0}^{n}{\begin{pmatrix}n \\i\end{pmatrix}{t^{i}\left( {1 - t} \right)}^{n - i}P_{i}W_{i}}}{\sum\limits_{i = 0}^{n}{\begin{pmatrix}n \\i\end{pmatrix}{t^{i}\left( {1 - t} \right)}^{n - i}W_{i}}}};$ there isat least one third control point between the third initial point and thethird terminating point, wherein P_(i) represents a position coordinateof an i^(th) point in the Bezier curve function; when a total number ofat least one third control point is one, a position coordinate of thethird initial point is (X₃,Y₃), a position coordinate of the thirdcontrol point is (X₄,Y₄); and a position coordinate of the thirdterminating point is (X₅,Y₅); wherein n represents the total number ofthe at least one third control point plus 1; W_(i) represents a weightof the i^(th) point; and t represents a ratio of a length between apredetermined point and the third initial point to a total length of thethird profile curve; wherein constraints of the second profile curve areX₃=X₅; Y₃≧Y₄≧Y₅; and 0≦W_(i)≦1.
 7. The light guide element of claim 1,wherein the first reflecting surface is formed from a plurality of firstreflecting curved surfaces, wherein each of the first reflecting curvedsurfaces is constructed by the first profile curve.
 8. The light guideelement of claim 1, wherein the second reflecting surface is formed froma plurality of second reflecting curved surfaces, wherein each of thesecond reflecting curved surfaces is constructed by the second profilecurve.
 9. A lamp, comprising: a light guide element being an annularfrustum, comprising: a light-incident surface having a first outerperipheral edge and a first inner peripheral edge; a light-emittingsurface which is opposite to the light-incident surface and has a secondouter peripheral edge and a second inner peripheral edge; a firstreflecting surface connecting the first outer peripheral edge and thesecond outer peripheral edge, wherein the first reflecting surface is acurved surface constructed by a first profile curve, wherein the firstprofile curve is a connecting line from a first initial point on thefirst outer peripheral edge to a first terminating point on the secondouter peripheral edge; and a second reflecting surface connecting thefirst inner peripheral edge and the second inner peripheral edge,wherein the second reflecting surface is a curved surface constructed bya second profile curve, wherein the second profile curve is a connectingline from a second initial point on the first inner peripheral edge to asecond terminating point on the second inner peripheral edge; and alight source, wherein a light generated from the light source enters thelight guide element from the light-incident surface and emits out of thelight-emitting surface to generate a predetermined light beam angle ofthe light.